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COMPLETELY SELF PROTECTED

DISTRIBUTION TRANSFORMER

BY :K. SUSHEEL KUMAR(06M21A0251)P. VINAY KUMAR (06M21A0257)G. MANIKANTA(06M21A0210)

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ABSTRACT

The high rate of failure of secondary distributiontransformer in power systems may perhaps bedescribed as 0ne of the tragedies of distribution

system management of present times especially indeveloping countries like India. The advent of CSPtechnology has encouraged progressivemanufactures to go in for high performance

distribution transforms which mitigate the operationand maintenance problems associated withconventional transformers. CSP technology enables

a transformer to protect itself from faults

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Aspects Covered In This

Presentation

what is CSP? & what is its purpose?

Why CSP transformer?

Reasons for failure of distribution transformer?

What is the philosophy of CSP?

Components of the CSP transformer

Major advantages of CSP transformer

Technical specification & IS specification of CSP

components.

Arriving at a conclusion

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What is CSP? & its purpose?

CSP is completely self protected transformer.

CSP is a protection system for distribution transformers.

Purpose of CSP:

It avoids major damages to the transformers by powersystem faults, by disconnecting the transformer (on eitherside) from faulty circuit.

The CSP protection system protects the transformer fromlightning, secondary faults, severe overloads and provides

visual warning of the existences of uneconomical loadingconditions

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Why CSP transformers?

Due to the higher failure rate of secondarytransformers in power system, especially indeveloping countries like India, kenya.

Short circuit faults. Excessive heat generation.

Excessive Current flow with out short circuit

faults due to change in resistance of the circuit. Protection against lightning .

Over loads on secondary.

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What is the failure rate of

distribution transformers?

In India 20%

In the west

1 to 2%

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Reasons for failure of distributiontransformers.

Changing weather conditions

Lengthy low voltage lines

Short circuit due to clashing of looselystring LV lines.

Lightning

Oil leakages Ingress of moisture etc.,

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What is the Remedy

Adopting CSPT is one of the options toreduce failure rate.

Proper maintenance

Proper design by considering atmosphericconditions

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What is the philosophy of CSP

Distribution transformer must be protected from over

loads

Electrical distribution system must be protected from

interruption in case of transformer failures

Distribution transformer should not be operated

regularly on over loads Lightning Arrestors are directly mounted on the

transformer tank to maximize surge protection

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Components of CSPT

Primary side : high voltage fuse

Secondary side : For over load secondary fault

protection

Surge arrester : for lightning protection

Signal light

Emergency control: magnetic trip Magnetic trip

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Primary ( high voltage fuse )

Power utilities in India provide a HV fuse on primaryside of a distribution transformer for systemprotection

Internally mounted

Rating determined such that it should not blow forsecondary faults and exciting current surges

Generally rated 12 times the full load current for 10msec

Connected in series with HV winding It protects the transformer from its internal faults

Protect the part of the electrical distribution system

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Secondary ( low voltage ) circuit

breaker

The low voltage circuit breaker is the centralcomponent of the CSP protectionpackage. Itprovides the entire over current protection to thetransformer.

Central component of the CSP protection package

Provides over current protection

Mounted internally

CB is of thermally operated type Responds to the secondary faults extermal to the

transformer by tripping open.

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Surge arrester

surge arrester is directly mounted to the

transformer tank.

The ground lead length is effectively zero and

maximum transformer protection is obtained.

lightning arresters are basically non linear

resistors i.e acts as resistors at operating at

voltages and as conductor at higher voltages.

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Constructional features:

Circuit breaker is an electromechanical device

and is of simple construction.

It has following major elements

Temperature sensing

Latching and tripping

Current interrupter

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Temperature sensing function:

Bi metallic strips, which are built into the breaker such thatload current flows through them.

Bi metallic strips responds thermally to the temperature oftransformer oil & temperature changes created by the flow ofload current through them

Latching and tripping function are carried out with anassembly of parts similar to those used in industrial type

If circuit breaker does trip in response to even a temporarysecondary fault, service can be restored easily by clearing thefault and re-closing the circuit breaker

Indication will be provided by the signal lamp for continuousoverload & trip

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Magnetic trip:

Certain circuit breakers are furnished with

magnetic trip which increases the opening

speed under high fault conditions.

There must be co ordination between primary

fuse element and secondary circuit breaker,

such that for any fault on the load side the

circuit breaker clears the circuit, fuse melts.

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Pressure relief device:

It operates at pre specified pressure.

Generally operates at 3.6 PSI, for corrugated

construction at 10 PSI for radiator construction

It releases the pressure at above value and

protect the tank from excess pressure.

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Technical specification:

Single phase : CRGO. Up to 167KV

AMT.. Up to167 KV

Three phase : CRGO. Up to 315 KV

AMT. Up to 315 KV

No of phases : single or three phase

Applicable standards: IS, IEC, ANSI, JIS, BS. Cooling : ONAN,OA

Insulating fluid : mineral oil to specification

Frequency : 50 or 60 HZ

Vector group : As specified Primary voltage : up to 11KV

Secondary voltage : 415, 433 volts or other

Winding material : copper or aluminum

Tappings : + or 5% or other

Impedence : as per appliclble standards

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What are the major advantages of

CSP technology

Enables a transformer to protect itself from faults

Transformer is protected from persistent overloads

not cleared by conventional protective gear.

Uneconomical over loading on a regular basis isavoided

Protection from lightning is most effective

No scope of ingress of moisture Failure due to undue pressure rise will not be there.

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Benefits

Low installation cost

Simple easy installation

Safe operation Reliable service

Low cost of operation

Clean appearance

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Is specifications of CSP components

Distribution T/F : 1180

Metal oxide surge arrester ; IEC- ANSIEEEE-C-11/1982

Circuit breaker : 13118

HV fuse link : 9385

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conclusion:

Thus CSP technology has paved the way tohigh performance distribution transformers and

better distribution management.